Re: [PATCH 0/2] Add support for Microchip EMC1812

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 25 Sep 2025 07:32:22 -0700
Guenter Roeck <linux@roeck-us.net> wrote:

> On Thu, Sep 25, 2025 at 09:09:04AM +0000, Marius.Cristea@microchip.com wrote:
> > Hi Guenter,
> > 
> > Thank you for the feedback.
> > 
> > On Tue, 2025-09-23 at 19:11 -0700, Guenter Roeck wrote:  
> > > EXTERNAL EMAIL: Do not click links or open attachments unless you
> > > know the content is safe
> > > 
> > > On 9/20/25 04:33, Jonathan Cameron wrote:  
> > > > On Wed, 17 Sep 2025 15:21:56 +0300
> > > > Marius Cristea <marius.cristea@microchip.com> wrote:
> > > >   
> > > > > This is the iio driver for EMC1812/13/14/15/33 multichannel Low-
> > > > > Voltage
> > > > > Remote Diode Sensor Family. The chips in the family have one
> > > > > internal
> > > > > and different numbers of external channels, ranging from 1
> > > > > (EMC1812) to
> > > > > 4 channels (EMC1815).
> > > > > Reading diodes in anti-parallel connection is supported by
> > > > > EMC1814, EMC1815
> > > > > and EMC1833.
> > > > > 
> > > > > Current version of driver does not support interrupts, events and
> > > > > data
> > > > > buffering.  
> > > > Hi Marius,
> > > > 
> > > > For a temperature monitoring device like this, the opening question
> > > > is
> > > > always why not HWMON?
> > > > 
> > > > There are various reasons we have temp sensors in IIO but mostly
> > > > they are not
> > > > described as being monitors and this one is.
> > > > 
> > > > IIO may well be the right choice for this part, but good to lay out
> > > > your
> > > > reasoning and +CC the hwmon list and maintainers.  There is an
> > > > emc1403
> > > > driver already in hwmon, so perhaps compare and contrast with that.
> > > > 
> > > > I've +CC Jean, Guenter and list to save sending a v2 just to do
> > > > that.
> > > >   
> > > 
> > > At first glance it looks like the series is (mostly ?) register
> > > compatible
> > > to the chips supported by the emc1403 driver, so it should be
> > > straightforward
> > > to add support for the emc180x series to that driver.
> > > 
> > > Guenter  
> > 
> > Most of the register address are compatible. The EMC181X is an update 
> > (a newer generation) then the EMC1403.
> > 
> > The biggest improvement is that the EMC18XX has a continuous block of
> > registers in order to improve the temperature reading (that means some
> > addresses are overlapping with the older register maps) and a new set
> > of registers to  handle the "Rate Of Change" functionality.
> > Also the older EMC14XX has some hardcoded configuration/features based
> > on the part number.
> > 
> > Considering all of the above I consider that the complexity of the
> > EMC1403 will increase quite a lot without any real benefit and it will
> > be harder to be maintained.
> >   
> Ok.
> 
> > I have submitted this as the fist iteration from a longer list of
> > feature that I want to add to the driver, including events and maybe
> > interrupts.
> > 
> > If nobody has anything against, I would like to add a separate driver
> > for EMC18XX into the IIO.  
> 
> IMO this should be a hwmon driver.

So far I haven't seen any reason why IIO would make more sense, so agreed.

Jonathan

> 
> Guenter